The objective of this project is to determine, by the X-ray crystallographic techniques, the three-dimensional structure of the enzyme L-asparaginase from the bacteria Proteus vulgaris. The goal for the three-year funding period is to establish the structure at 3A resolution. The molecule is believed to be composed of four chemically identical subunits and has a molecular weight of 120,000. It is capable of causing remission of acute lymphoblastic leukemia and immunologically distinct from the enzyme from E. coli. So far the study has progressed to establish the following: 1) Space group P21, a equals 69.3A, b equals 125.6A, C plus 101.4A, beta equals 90 degrees 20', Z equals 2 tetramer. 2) The subunits are geometrically identical at the level of approximately 10A --they are related to one another by a D2 group pseudo-symmetry. 3) The molecular center is located at x equals 0.054, y equals 0, z equals 0.256. The centers of the subunits are probably near x equals 0.17, y equals -1/8, z equals 0.10 and its pseudo-symmetry related positions. 4) Platinum-, osmium, and gold-containing heavy atom agents give significant changes in the X-ray diffraction pattern. 5) A platinum position has been found on a difference Patterson map.